基于线型腔光纤激光器的变压器局部放电长距离检测技术

Power Transformer Partial Discharge Long-distance Detection Technology Based on Linear Cavity Fiber Laser

用于电力设备局部放电检测的传统光纤声波传感器,因受灵敏度、介质相融性、难以与解调系统空间分离等因素影响尚未广泛应用。线型腔光纤激光器(linear cavity fiber laser,LCFL)因具有超窄出射线宽而对高频应变具有极高的检测灵敏度,且其体积微小,敏感单元与解调系统相互独立,可有效解决传统光纤声波传感器所面临的上述问题。该文提出并研制基于线型腔光纤激光器技术的局部放电声波检测系统。为解决LCFL光源本征特性在局部放电长距离检测应用中引入的外部光反馈噪声问题,利用半导体激光器外部光反馈理论确定光隔离器的安装位置,使LCFL工作于外部光反馈系数A区(0~200.6m)对系统进行优化,将系统长距离条件下的平均噪声幅值降低了87.49%。在80kVA油浸式变压器绕组长距离传导光纤局部放电检测平台开展实验,结果表明:所研究的LCFL局部放电检测系统在最大超声衰减情况下可有效应用于局部放电长距离检测。在相同超声激励源下,LCFL系统平均最大响应幅值比压电陶瓷传感器(piezoelectric transducer,PZT)高1354%,且稳定性优于PZT。

Traditional fiber optic acoustic emission(AE)sensors used for power equipment partial discharge(PD)detection are still unsatisfactory in engineering due to the sensitivity,media compatibility,and difficulty in spatial separation from the demodulation system.The linear cavity fiber laser(LCFL)has ultra-high detection sensitivity because of its ultra-narrow linewidth emission.Moreover,the small size of LCFL and its independence from the demodulation system may effectively solve the above problems.This paper proposes a PD AE detection system using LCFL as the sensor.Then,the installation position of the optical isolator is determined in the A regime(0~200.6m)of external optical feedback(EOF)coefficient based on the EOF theory of semiconductor laser to suppress the EOF noise introduced by the intrinsic light source property of LCFL in the long-distance application.The average noise of the improved system in long-distance detection is reduced by 87.49%.The experimental results of 80kVA oil-immersed transformer PD long-distance detection show that the PD detection system could be effectively applied in PD long-distance detection with sizeable ultrasonic attenuation.The average maximum response amplitude of the system is 1354%higher than that of the piezoelectric transducer(PZT)sensor during the same AE excitation,and the system stability is much better than PZT.